| | Mount Morris, IL | Morris, IL | United States |
| Population | 3,044 | 14,601 | 329,725,481 |
| Female Population | 55.0% | 51.1% | 50.5% |
| Male Population | 45.0% | 48.9% | 49.5% |
| Median Age | 45.8 | 37.8 | 38.4 |
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| Population - 2010 | 3,005 | 13,664 | 309,327,143 |
| Population - 2000 | 3,013 | 11,928 | 285,036,114 |
| Population - 1990 | 2,919 | 10,270 | 251,960,433 |
| Pop. 2000 to Now | -7.9% | 27.1% | 15.6% |
| Pop. 1990 to Now | -4.9% | 47.6% | 30.8% |
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| Population Density | 1,834.8 | 1,451.3 | 93.4 |
| Land Area | 1.7 | 10.1 | 3,531,905.4 |
| Water Area | 0.0 | 0.4 | 264,836.8 |
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| Est. Total Population By Age | | | |
| | Mount Morris, IL | Morris, IL | United States |
| Age 0 to 4 | 12.7% | 5.4% | 5.9% |
| Age 5 to 9 | 10.2% | 9.0% | 6.1% |
| Age 10 to 14 | 2.3% | 5.3% | 6.6% |
| Age 15 to 17 | 0.0% | 3.2% | 3.9% |
| Age 18 to 20 | 0.0% | 2.6% | 4.0% |
| Age 21 to 24 | 1.8% | 5.8% | 5.2% |
| Age 25 to 34 | 16.7% | 14.2% | 13.8% |
| Age 35 to 44 | 5.3% | 12.4% | 12.9% |
| Age 45 to 54 | 11.0% | 13.2% | 12.6% |
| Age 55 to 59 | 6.0% | 6.8% | 6.7% |
| Age 60 to 64 | 2.7% | 5.6% | 6.3% |
| Age 65 to 74 | 11.3% | 9.5% | 9.6% |
| Age 75 to 84 | 8.6% | 4.0% | 4.5% |
| Age 85 and over | 11.3% | 3.1% | 1.9% |
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| Race | | | |
| | Mount Morris, IL | Morris, IL | United States |
| White | 97.2% | 83.2% | 59.4% |
| Black | 1.4% | 0.4% | 12.2% |
| Asian | 0.0% | 0.6% | 5.6% |
| Native American | 0.0% | 0.0% | 0.6% |
| Hawaiian, Pacific Islander | 0.0% | 0.0% | 0.2% |
| Other | 0.0% | 1.0% | 0.4% |
| Two or More Races | 1.4% | 3.8% | 3.2% |
| Hispanic | 0.0% | 10.9% | 18.4% |
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| Marriage & Family | | | |
| | Mount Morris, IL | Morris, IL | United States |
| Married Population | 47.2% | 52.0% | 49.8% |
| Currently Married | 44.3% | 50.3% | 48.0% |
| Married but Separated | 2.9% | 1.7% | 1.8% |
| Single Population | 52.8% | 48.0% | 50.2% |
| Never Married | 20.5% | 30.2% | 33.8% |
| Divorced | 15.4% | 11.4% | 10.8% |
| Widowed | 16.9% | 6.4% | 5.6% |
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| Household Size | 1.98 | 2.33 | 2.60 |
| Households | 1,484 | 6,106 | 124,010,992 |
| Family Households | 684 | 3,800 | 80,755,759 |
| Married couple, w/children | 12.3% | 30.0% | 30.5% |
| Married couple, no children | 51.3% | 43.6% | 42.9% |
| Non Family Households | 800 | 2,306 | 43,255,233 |
| Single householder, w/children | 27.3% | 17.4% | 15.8% |
| Single householder, no children | 9.1% | 9.0% | 10.8% |